Star Cluster Simulator 4+

The single problem with a super realistic star simulation on mobile is that it is on mobile, which doesn’t have nearly as much processing power as a computer. I am personally playing on an iPhone 7 which isn’t the latest by any means but it literally didn’t load ANYTHING, then the screen started glitching and my phone crashed. It might be a good simulator but if you don’t have a newer iPhone or iPad, don’t even bother.

Not expecting this simulation to be perfect by any means. But no matter what settings or for however long I let it run, it never produces anything resembling an accretion disk or galaxy at all. All it does is eventually fling all the particles away from the central point, gradually dispersing them evenly (or somewhat) across the whole space.

The screenshot they have of a galaxy is likely a freeze frame taken right when the program runs while everything is still in a disk form to some extent. If you ran it with the settings shown in the screenshot, you’ll just end up with stars evenly spaced everywhere mostly moving away from the central starting point.

It would be really fun if they did explode out and then gradually coalesce into some kind of recognizable stellar formation but no, it never will. And part of this is likely due to the calculations not accounting for dark matter as well as none of the points joining together to create larger stars. Astrophysicists have a hard time calculating/predicting formation and movement of stars in an actual galaxy so I’m not surprised that it’s basically impossible to do even at this scale.

So for me, one star. Because the app is lying about what is possible.

Prove me wrong and I’ll change the rating. But for now, don’t bother downloading.

overall stars rating 4.
High stars for ambition
Zero stars for no help or manual
low stars for user interface (but this could be because of no help)

First let me say that this app DOES work. Hints: Use “i” on the starting point (the colored disk) to set up model, use lots of stars (32K is not too many). Turn the brightness up, zoom out and speed it up. The grid can be tuned on and off and I found if necessary to get proper stereo fusion. It did require QUITE a bit of fiddling around on a high performing platform to figure it out. Some background in NBody simulation was also helpful.

Tested on an iPhone 13 pro max, an iPad7 and running on the 14” M3 macBook Pro (iPhone app emulator). It worked on all three. Performance on the iPhone was good, macBook very good, but the iPad7 was, as expected poor. Bizarrely, the app did not trigger the performance cores on the macBook Pro, but I suspect this is a function of the emulator. Running on the MacBook, it consumed less than 7% of the available processor capacity. A port to apple silicon MacOS could be spectacular in performance, even if not muti-threaded.

An N body simulator on a mobile device is a pretty cool idea! the tree code algorithm implemented here is an obvious choice. My congratulations to the author on getting it to work! A labor of love.

That said, the user interface is rather non-standard relative to Apple iOS expectations. This is not a problem IF there is explanation on how things are supposed to work, but this app does not provide one. I suspect that this is the cause of the low ratings and bad reviews.

Although things seemed to be OK, I was not able to figure out if it actually is simulating accurately. As expected, the spherical model appeared to work best. This is probably a good approximation of a galaxy with a spherical halo of invisible “dark matter” particles. There is apparent loss of some stars as they get thrown out by close interactions. It was not possible to tell if this was OK as there is not indication of energy conservation in the simulator.

Suggestions:
1) Some help! Doesn’t have to be in other than the author’s language as long as it is machine translatable.
2) Provide some indication if the generated system is expected to be an enegetically bound system. It would be good to somehow indicate stars attaining escape velocity. (by color?)
3) Color code the spherical system so that stars that start in the plane of the distribution can be distinguished from the others. This would mark the “halo” stars as dark matter and the others as baryonic stars.